Water-repellent and vapor-permeable multilayer material for outdoor applications

ABSTRACT

The invention relates to a multilayer material comprising (a) a first layer that consists of plaster or that substantially consists of plaster, and (b) at least one second layer, comprising a sandwich textile fiber material. The fibers of said material are interlinked in a mechanically stable manner, are incombustible and weather-proof and the interspaces are filled with a finely porous material. The second layer has a diffusion-equivalent air layer thickness of not more than 2.0 m and is water-impermeable at a water pressure of at least 100 mm water column. The inventive material can be used outdoors due to its properties. The invention further relates to methods for producing such a material.

This application is a 371 of PCT/EP02/02028 filed on Feb. 25, 2002, theentirety of which is hereby incorporated by reference.

This invention relates to a multilayer, preferably sheet-like materialwith a gypsum core for outdoor applications which is coated at least onone side such that it has water-repellant properties at least on thisside, but remains vapor-permeable. The material is suitable for outdooruse, for example weather-resistant use in building construction.

Gypsum has very favorable material properties which make it attractivefor construction applications. This includes natural moistureequalization with the environment, a low water vapor permeationresistance, good fire resistance behavior, no emission of toxicsubstances, a low specific weight and low production costs. One decisivedisadvantage is the poor resistance to water, since gypsum hasrelatively high solubility in water. Even if there is only the danger oflonger moisture absorption of plasterboard, use of gypsum materials isnot allowable. Gypsum tends under these conditions to creep deformation,and irreversible damage to the gypsum structure occurs, which is alsocalled rotting. For this reason structural panels for outdoors whichconsist mainly of gypsum and are directly exposed to the weather havenot been known to date.

Various forms of plasterboard for interior applications are available onthe market. Gypsum plaster board is especially widely used. The gypsumcore sheet is lined on both sides with a cardboard layer. Onedisadvantage of the gypsum plaster board is the high flammability of thecardboard, another is low water resistance. In order to achieve agreater fireproof character, DE OS 28 08 723 proposed a plasterboardwhich is lined with a glass fiber veil. Inorganic particles can be mixedinto the binder of the glass fiber veil, which binder holds the fibersof the veil together. Thus DE 31 13 682 A1 describes the use of certaininorganic hydroxides in the binder to cause chemical bridge formationwhen thin plaster which has been applied in liquid form sets, by whichbridge formation the strength of the connection between the jacket andthe gypsum core is improved. The additive moreover improves thefireproof property of the plasterboard. DE 35 06 933 A1 proposes placingon one side of the gypsum core a glass fiber veil which is coated on itsoutside with an artificial resin adhesive such that the coating can beused as reinforcement against wear. For purposes of fireproofing,discrete inorganic particles are mixed into the organic binder, alsoimproved air and vapor permeability being achieved. A veil with asimilar structure is also described by DE 34 08 932 A1. It is coated onone side with an inorganic powdered material and a binder, its having tobe watched that the open structure of the veil is preserved on the sidefacing away from the coating in order to ensure good anchoring of theveil to the plasterboard. Patents DE 195 27 857 and DE 195 27 858proposed providing the glass fiber veil with an inorganic coatingconsisting essentially of calcium sulfate and containing an organicbinder and optionally other additives for production engineering reasonsand to increase the adhesive strength between the plasterboard and veil.One-sided coatings of the glass fiber veil are also proposed more oftento avoid the flow of the thin plaster through the veil and theassociated fouling of the conveyor belt in the subsequent production ofthe gypsum core sheet (see for example DE 39 37 433 A1).

The plasterboard which is proposed by manufacturers for outsideapplications includes products which may not be exposed either to directrainwater and which therefore require external protection (for example,heat insulating composite systems), or the structural panel consists ofgypsum only to a relatively small proportion. In the former case the useof plasterboard is associated with a relatively high cost. Conversely,in the latter case it is not a plasterboard in the sense of thisapplication, since a considerable or even predominant proportionconsists for example of cement (see DE 39 37 429 A1).

In addition, waterproofing agents are known which can be added to agypsum mass before setting (mass waterproofing) or are applied later tothe hardened product (surface waterproofing). In this way gypsumplasterboard can be produced which is suitable for use in wet spaces aswell. The action of this protective measure is however not sufficient toallow the plasterboard to be used outdoors, where it is exposed to heavyprecipitation in direct contact.

The object of this invention is to make available a plasterboard foroutdoor application which can be directly exposed to weather, but doesnot prevent moisture equalization of the gypsum and the borderingcomponents which are present under certain circumstances.

In achieving the object a multilayer material with a gypsum core sheetis made available which is provided on one side (which is intended asthe outside) or on the two sides with a protective layer which ispermeable to water vapor and thus further enables the moistureequalization of gypsum, but on the other hand keeps liquid water fromcoming into contact with the gypsum and has improved airtightness. Thiswater-repelling and vapor-permeable protective layer comprises a textilefabric of mechanically stable fibers which are not flammable and areweather-resistant, in combination with a water-insoluble material whichhas fine pores, which is located within the fiber layer and fills itsintermediate spaces such that the protective layer is pressure-tight forliquid water of at least 100 mm water column, water vapor conversely isallowed to pass as a result of a favorable, diffusion-equivalent airlayer thickness of distinctly less than 2.0 m, especially of less than1.0 m, and is water-insoluble at least on its outer side.

The fiber material for the textile fabric is not limited if it has thenecessary properties. Inorganic fibers such as for example glass fibersor mineral, especially ceramic fibers, are well suited. The structure ofthe fabric is not critical if the fibers are mechanically stably joinedto one another. Thus textiles, woven fabric, knit, nonwovens or the likecan be used. The fibers can be fixed among one another using a binder,which preferably, but not necessarily, is an organic binder. A wellsuited binder material is melamine resin. A textile fiber material whichis especially preferred as claimed in the invention is a glass fiberveil especially of E glass, with fibers which have been fixed withmelamine resin. These materials have good weather resistance.

Because the textile fiber material is filled with a fine material whichhas open pores, the second layer of the multilayer material remainspermeable (diffusion-open) to gaseous water. This is because thepermeability of gases is dependent solely on the presence of pores andtheir size, but not on the chemical properties of the material whichforms these pores. It is different with the permeability to liquidwater: this is determined not only by the pore size, but also by thehydrophilia/water repellency of the material. A criterion which isnecessary for the invention is therefore naturally that the materialshould not have coarse cracks or holes through which liquid water couldpenetrate into the board even if the material used were relativelywater-repellent. This is achieved in that the fiber material is filledwith a material which has fine pores. This coating cannot be achievedsolely by coating with a pasty mass, for which reason it is a good ideato precipitate a polymer directly in the fiber material or to impregnatethe fiber material with a dissolved or dispersed/suspended polymer orits precursors, then to remove the solvent and optionally inducecross-linking of the material.

As mentioned above, the property of the second layer to bewater-repellent or to prevent the passage of water is determined notonly by the pore sizes, but also and mainly by the water repellency ofthe material which has fine pores. Water-repellent materials as havebeen used in the past to coat glass fiber veils, and which are describedfor example in the aforementioned documents DE 34 08 932 A1 and DE 35 08933 A1, are therefore not suited for this invention even if they havepores and thus have a certain air permeability. These materials areinorganic materials such as calcium carbonate, aluminum hydroxide andoxide hydrates, perlites, limestone, gypsum, or vermiculite or the like.They are not only all hydrophilic, but also partially even hygroscopic.

The expression “material which has fine pores” as claimed in theinvention is defined as a material with pores of dimensions such thatthe passage of liquid water is prevented, the passage of gaseous water,therefore water vapor, is however possible. Since these properties aredependent not only on the dimensions of the pores as such but also onthe properties of the pore-forming material, especially its hydrophiliaor water-repellency, the pores of water repellent material can be largerthan those of more hydrophilic material without losing the desiredeffect. Accordingly the expression “fine pores” should encompass poreswith pore sizes from the nm to micron range if the material surroundingthem is water-repellent enough to prevent the passage of water. Thiswater repellency can be determined for example by the edge angle of awater droplet which rests on the material to be determined. For thisinvention especially those materials are suitable on which a waterdroplet stands with an edge angle from 80° to 140°, preferably from 95°to 130°.

The material which forms the fine pores can be an inorganic, an organicor an inorganic-organic polymer material or can be formed on the basisof mixtures of these materials. Polymers which are suited for thisinvention are essentially insoluble in water, but still have sufficientwater repellency to form a coherent, fine-porous layer in the presenceof water. Another desired criterion is sufficient UV stability so thataromatic compounds can be used only conditionally, i.e. with thecorresponding stabilization. Preferably the organic polymers canaccordingly include oxygen-containing materials, for example polymerswhich contain ester groups such as polyesters, cellulose esters andderivatives of starch, copolymers with vinyl acetate such asethylene-vinyl acetate copolymers (EVA), but also for examplepolyurethanes of aliphatic or cycloaliphatic diisocyantes. Acidgroup-containing copolymers such as copolymers based on maleic acid oracrylic or methacrylic acid are examples of these oxygen-containingpolymers with hydrophilic properties. Furthermore, cross-linked polymerswhich are present first as oligomers during application and crosslinkand become insoluble in water only after layer formation can be used asa material which forms fine pores.

Inorganic-organic or also purely inorganic materials can be used. Oneexample is water glass which is chemically hardened for example usingmultivalent cations or phosphates, especially aluminum phosphate. Bychemical hardening it achieves high water resistance. Inorganic polymersfurthermore include the so-called geopolymers. i.e. mostly amorphous tosemicrystalline, three-dimensional silicon aluminates which can beproduced by so-called geosynthesis, i.e. at temperatures belowconventional sintering temperatures, generally distinctly below 450° C.They can be obtained for example from surfactant fillers, so-calledphyllosilicates (kaolinite, montmorillonite, halloysite) withconcentrated sodium hydroxide solution or water glass and can contain 8and/or 12 membered-rings of Si, Al, and O. These geopolymers aredescribed for example in detail in the “Journal of Materials Education”,V. 16 (283), pp. 91-139 (1994) or in Alkaline Cements and Concretes,KIEV, Ukraine, 1994. Properties of Geopolymer Cements. Since it partthey harden even below 100° C. (set, condense), they are also calledcold setting ceramics.

Both water glass and also the geopolymers can be made water repellent ifnecessary, for example subjected to mass waterproofing.

It is an especially good idea to use a mixture of organic and inorganicmaterial.

There is a series of various possibilities for filling the textile fibermaterials with a material which forms fine pores. Processes areespecially favorable by which the fine-porous material in the fibernonwoven or the fiber mat is precipitated, or processes in which thenonwoven or the mat is impregnated with a solution, suspension ordispersion from which the fine-porous material is formed or remainsafter removing the solvent.

In one embodiment of the invention, accordingly a fine-porous structureis produced in the flat, textile fabric in that the fiber layer isimmersed in a solution of a polymer which is soluble in an organicsolvent. After removing the fiber layer from the solution it is driedfor a certain time in air and then dipped into a solvent, for example awater bath, in which the polymer is not soluble and thereforeprecipitates. In doing so a fine-porous layer forms in the fiber layer.The process can optionally be repeated until sufficient filling isachieved (i.e. there are no longer any large holes or pores in the fiberlayer). After removal from the water bath the filler fiber layer iscompletely dried. The fine-porous layer produced in the fabric has awater-repellent effect with a suitable selection of the polymer withsimultaneous permeability to water vapor. The water-repelling action canbe recognized in that a water droplet on the fiber surface does notpenetrate into the layer, but forms a clear edge angle.

Polymer materials which can be used to form a fine-porous structure inthe textile fiber material layer using this process are for examplecellulose propionate, cellulose butyrate and copolymers of ethylene andvinyl acetate. In the ethylene-vinyl acetate copolymer the solubility inthe solvent (acetone is suitable) depends on the proportional ratio ofthe two monomers. A mass ratio of the two monomers of 20:80 or of 40:60can be used. With an ethylene-vinyl acetate copolymer with a mass ratioof 20:80 a fine-porous layer can be produced in a glass fiber veil whichprevents penetration of water at a water height of 150 mm.

In another embodiment of the invention a fine-porous structure in thetextile fiber material layer is produced by the layer being immersedonce or optionally several times in a polymer dispersion and being driedafter it is removed. The polymer dispersion consists for example ofsmall polymer particles (dispersed phase) in water (continuous phase).In the production of a fine-porous layer in the fiber layer film-likestructures form between the fibers and prevent passage of water. Oneexample of production of a fine-porous layer using this procedure is useof an aqueous acrylate dispersion. A glass fiber veil filled in this waywith an acrylate dispersion could prevent a water column with a heightof more than 400 mm from passing through the veil.

In another embodiment of the invention the textile fiber layer istreated with a solution or suspension of an inorganic material.Solutions of water glass and/or one of the aforementioned geopolymersare especially suited for this purpose. Geopolymers can be subjected toa condensation reaction at relatively low temperatures afterimpregnating the fiber material with a solution which contains thecorresponding starting materials, for which reason they are especiallywell suited for this invention. In part, the setting takes place even atroom temperature and at least at such mild temperatures that the binderwhich may be contained in the textile fiber material is not damaged.When the geopolymer which is being used has not been subjected to priormass waterproofing, it is preferred that its water repellency beincreased later, for example it being made water repellent using surfacesilanization, in order to make the surface water-repellant.

The textile fiber material can be joined to the gypsum core by coatingor in some other way. It is a good idea if the textile fiber material isfirst impregnated with the material which has or forms the fine poresand after setting or drying of this material the fiber material isplaced on a base and is painted or otherwise coated with the thinplaster which optionally contains additives. When the gypsum sets anintimate bond of the plasterboard with the textile fiber material forms.Alternatively the textile fiber material can be joined mechanically, forexample by clamping, to the already hardened plasterboard. Cementing isalso possible, its having to be watched that a continuous cement layeris not produced which inhibits the passage of the water vapor.

The gypsum core sheet which acts as the carrier sheet has a matrix ofgypsum (calcium sulfate dihydrate, CaSO₄x2H₂O). The sheet can consistexclusively of gypsum, but generally also contains reinforcing particles(for example, fibers or chips), often also water-repelling agents andoptionally other additives which are known to one skilled in the art.They include for example setting delaying agents, setting accelerators,substances which influence rheology, or pore agents. The gypsumproportion in the sheet is for example preferably 50-100% by weight,more preferably roughly 78-97% by weight, and especially preferably 80and 93% by weight.

It is often desirable to provide the plasterboard with masswaterproofing based on silicones, paraffins, waxes, artificial resins orthe like, as is known for use in wet spaces. Mass waterproofing isdesigned to prevent larger amounts of water from collecting on theinside of the textile fiber material and the gypsum structure fromdissolving and being destroyed over time.

Especially economical mass waterproofing can be achieved by using solids(paraffin, wax, microcapsules) with a water-repellent effect. To dothis, fine-particulate waterproofing agents can be added directly to thefresh mass of a settable calcium sulfate, and optionally to thereinforcing particles. In order to uniformly distribute thewaterproofing agent in the matrix the material can be subjected tocontrolled heat treatment following the hardening of the calciumsulfate. In this heat treatment the solid waterproofing agent melts andthe matrix is impregnated from the inside out. Heat treatment can takeplace in a continuous drier or by means of a high frequency or microwavetreatment. Solid waterproofing agents are especially advantageous whenliquid waterproofing agents adversely affect the hydration behavior ofthe calcium sulfate.

To increase strength, the plasterboard can also contain reinforcingparticles, for example, fibers or chips, preferably in a proportion of0.5-35% by weight, more preferably in a proportion of 1-30% by weightand especially preferably in a proportion of 5-25% by weight relative tothe amount of gypsum-containing dry mass which is used to mix the thinplaster. The reinforcing particles can consist of organic or inorganicmaterials such as glass or cellulose or can contain these materials asthe core. The chips or fibers can optionally be surface-modified toimprove adhesion, for example by modification with silanes. Moreover thegypsum core sheet can be provided with lightweight fillers such asperlite or can be foamed using a pore forming agent such as for examplethe sodium salt of an olefin sulfonate (for example Hostapur OSB,Hoechst) in order to reduce the weight and to increase the thermalinsulation capacity. The additives yield a moisture behavior such thatthe water vapor diffusion resistance decreases with increasing materialmoisture content so that a wet sheet dries out more quickly than onewhich is less wet and in another case a dry sheet absorbs moisture moreslowly.

To produce the water-repellent property and vapor permeability thegypsum core sheet as claimed in the invention is combined as mentionedat least on one side with the textile fiber material, with intermediatespaces which are filled with a material which has fine pores. Here itmust be watched that the respective production process takes place attemperatures which preclude damage to other components of theplasterboard. This means that when the material which has the fine poresis to be made as a filler material only in the textile fabric, this musttake place at a low temperature such that no damage occurs to thematerials which may already be contained in the fabric, such as organicbinders.

With the described measures multilayer material sheets are producedwhich withstand a water pressure of more than 1000 Pa, preferably morethan 1500 Pa on the veil-lined side without water passing through theveil. The water absorption coefficient is distinctly below 0/5kg/(m²√t). The diffusion-equivalent air layer thickness at a sheetthickness of 0.1 m is much less than 1.0. In preferable embodiments ofthe invention it is 0.6, more preferably 0.3 and in especiallypreferable cases even less than 0.2 m.

The invention is detailed below using examples.

EXAMPLE 1

A melamine resin-bonded veil of E glass fibers with a pore width betweenthe fibers of roughly 10-100 microns is immersed in a solution of 50 gcellulose propionate in 950 g acetone for 0.5 minutes. After removalfrom the solution, the excess solution is allowed to drip off and someof the acetone is evaporated. After 2.5 minutes the veil is immersed ina water bath and allowed to remain there for 6 hours. Then the veil isdried for 16 hours in a drying cabinet at 40° C. The dried veil isplaced on a flat metal plate onto which a frame 1 cm high is screwed.The flame is filled with a paste of plaster to which a 0.5% of asilicone waterproofing agent are added during mixing. The thin plasteris distributed in the frame by shaking. The excess amount is removed byscraping. After a setting time of one hour the frame is removed. Theplasterboard is dried for 24 hours in ambient air and for another 24hours in a drying cabinet at 40° C.

EXAMPLE 2

A melamine resin-bonded veil of E glass fibers is immersed for oneminute in an aqueous polyacrylate dispersion. After removal from thedispersion some of the excess liquid is allowed to drip off. On a flatbase the remaining dispersion is scraped off the veil surface on bothsides. Then the veil is dried for 24 hours in a drying cabinet at 40° C.The dried veil is placed on a flat metal plate onto which a frame 1 cmhigh is screwed. As is described in example 1, the frame is filled withgypsum and the gypsum is dried after setting.

EXAMPLE 3

A melamine resin-bonded veil of E glass fibers is painted with a mixtureof 45 g of a surface-reactive aluminosilicate powder, 55 g water glassand 5 g water (geopolymer mixture). The geopolymer mixture is uniformlydistributed on the veil by rolling. The coated veil is dried for 72hours in ambient air and another 24 hours in a drying cabinet at 40° C.The dried veil is placed on a flat metal plate onto which a frame 1 cmhigh is screwed. As is described in example 1, the frame is filled withgypsum and the gypsum is dried after setting.

EXAMPLE 4

To characterize the veil properties, a melamine resin-bonded veil of Eglass fibers with a pressure tightness of 0 mm water column and with apore width between the fibers of roughly 10-100 microns is immersed in asolution of ethylene-vinylacetate copolymer (concentration 5, 10 and 15%by M) and the polymer after different breathing times is caused toprecipitate. At a concentration of 5% and a breathing time of 1 min,after 5 coating processes a pressure tightness of 320 mm water columnwas reached. At a concentration of 5%, a breathing time of 1 min and acoating process the pressure tightness was 145 mm water column. Inneither case was any change of the water vapor permeability relative tothe untreated veil ascertained.

In all examples the composite sheet was examined for its diffusionproperties and its water repelling properties. The water vapor diffusionresistance numbers (μ value) were used as the standard for the diffusionproperties in the dry range, and for the water repelling properties thewater absorption coefficients (w values, kg/(m²h^(−1/2))) were used. Aplaster board (thickness 0.01 m) without waterproofing agents andwithout a veil has a μ value of 8 and a w value (1 h) of 3.90kg/(m²h^(−1/2)). With a conventional waterproofing agent (0.5% by M) a μvalue of 8 and a w value of 0.23 kg/(m²h^(−1/2)) were determined. For acomposite sheet with 0.5% waterproofing agent in the carrier sheet and aveil which has been treated as claimed in the invention, the w value was0.03 kg/(m²h^(−1/2)) and the μ value was 9.

1. A multilayer material comprising: (a) a first layer which consists ofgypsum or in essential parts of gypsum, (b) at least one second layer,comprising a layered textile fiber material with fibers which are joinedin a mechanically stable manner among one another, which are notflammable and which are weather-resistant, and its intermediate spacesare filled with a material which has fine pores, the second layer havinga diffusion-equivalent air layer thickness of less than 2.0 m and beingimpermeable to water at a water pressure of at least 100 mm watercolumn, wherein the material which has fine pores is selected from thegroup consisting of a partially or entirely an inorganic material. 2.The multilayer material as claimed in claim 1, wherein thediffusion-equivalent air layer thickness of the second layer is lessthan 1.0 m, preferably less than 0.2 m, and/or the layer is impermeableto water at a water pressure of at least 150 mm.
 3. The multilayermaterial as claimed in claim 1, wherein the gypsum layer furthermore hasreinforcing particles of inorganic or organic fibers or chips.
 4. Themultilayer material as claimed in claim 3, wherein the reinforcingparticles consist of glass, stone, cellulose, lignocellulose or mixturesof these materials or contain them.
 5. The multilayer material asclaimed in claim 1, wherein the partially or entirely inorganic materialis selected from the group consisting of a geopolymer and a materialwhich has been produced from water glass by hardening.